The present invention relates to an adapter device for connection of a low voltage switching device to a distribution bus bar system. The adapter device comprises a body provided with a front wall, which can be connected to the switching device, and a back wall, opposite the front wall. The device comprises first electrical terminals susceptible to electrically contact one of the distribution bus bars and second electrical terminals. The device also comprises first electrical connections electrically connected to first electrical terminals and which can be coupled with corresponding third electrical connections of the switching device. The adapter device is also provided with second electrical connection means connected to corresponding second electrical terminals and which can be coupled with corresponding fourth electrical connections of the switching device. The adapter device also comprises a plurality of coupling terminals, at least partly emerging from the back wall of the body, to removably connect the adapter device to the distribution bus bar system. In particular, each of the first electrical terminals electrically contacts one of the distribution bars following the action of one of said coupling terminals.